Catalyst component for use in the polymerization of .alpha.-olefins and process for producing .alpha.-olefin polymers using the same

A catalyst component for use in the polymerization of .alpha.-olefins which comprises a compound represented by the following formula [I]:

• ##STR16## wherein R.sup.1 s each independently represent a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms or a hydrocarbon group having 1 to 12 carbon atoms with a silicon atom contained therein;
• each of R.sup.2 and R.sup.3 independently represents a divalent group selected from the group consisting of a hydrocarbon group having 3 to 30 carbon atoms and a silicon-containing hydrocarbon group having 1 to 30 carbon atom and 1 to 6 silicon atoms, provided that at least one of R.sup.2 and R.sup.3 is said silicon-containing hydrocarbon group;
• Q represents a divalent hydrocarbon group having 1 to 20 carbon atoms, a silylene group, a silylene group with a hydrocarbon group having 1 to 20 carbon atoms, a germylene group, or a germylene group with a hydrocarbon group having 1 to 20 carbon atoms, which group combines the two five-membered rings with each other;
• X and Y each independently represent a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 20 carbon atoms, or a hydrocarbon group having 1 to 20 carbon atoms with an oxygen atom, a nitrogen atom, a silicon atom or a phosphorus atom contained therein;
• and M represents a Group IVB ti VIB transition metal of the Periodic Table, wherein each of R.sup.2 and R.sup.3 is the silicon-containing hydrocarbon group wherein the silicon is a member of the ring fused with the five membered ring.